Why is my UV Map in separate parts?
This is how Smart UV Project looks like.
I never checked the donut tutorial, so I don't know what's the base mesh you worked with, but when you start with blenders base mesh Torus object, it gives you nicely unwrapped UVmap into square already.

Basically to get more control over Unwrapping, you have to

Mark Seams Ctrl+E to let blender know where to split a net
(the edges marked by red color in screen, just select two edge loops with Alt+Shift select)



select all faces and Unwrap U &gt; Reset
select only one face and Unwrap U &gt; Follow Active Quads